1. Field of the Invention
This invention relates to a method of manufacturing semiconductor devices, particularly a method of forming films such as silicon oxide films in large scale integrated circuits (LSI).
2. Description of the Related Art
Chemical vapor deposition (CVD) method is a technology of forming thin films on substrates, which have been used widely in the semiconductor device industry.
Recently in this technology, a CVD method using an organic silane compound gas and an ozone gas is well-known as a method of forming thin films of silicon oxide.
But this method has several problems. Particularly, it serious problem that silicon oxide films formed by this method absorb water (H.sub.2 O) during the deposition of the films. This water is exhausted in the steps in the process of manufacturing semiconductor devices, and if conductive layers are formed on the silicon oxide films, serious problems, such as disconnection of the conductive layers, failure of contact between the conductive layers, and so on, are caused by the exhaustion of the water. Furthermore, the water absorbed into the silicon oxide films causes an increase of the dielectric constant of the silicon oxide films, and thus the reliability of the silicon oxide films as insulating layers is reduced.
The absorption of water vapor into silicon dioxide films formed by CVD methods is reported in Ann Marie Nguyen and Shyam P. Murarka: Properties of chemical vapor deposited tetraethylorthosilicate oxides: Correlation with deposition parameters, annealing, and hydrogen concentration (Journal of Vacuum Science Technology B8(3), May/June 1990).
As described above, the conventional process of forming silicon oxide films by CVD methods is encountered with a problem that water is absorbed into the films and that the reliability of semiconductor devices is seriously affected.